存储类

const Storage<QString> storage;

const auto onFirstDone = [storage](const Task &task) {
    // Assings QString, taken from the first task result, to the active QString instance
    // of the Storage object.
    *storage = task.getResultAsString();
};

const auto onSecondSetup = [storage](Task &task) {
    // Reads QString from the active QString instance of the Storage object and use it to
    // configure the second task before start.
    task.configureWithString(*storage);
};

const Group root {
    // The running task tree creates QString instance when root in entered
    storage,
    // The done handler of the first task stores the QString in the storage
    TaskItem(..., onFirstDone),
    // The setup handler of the second task reads the QString from the storage
    TaskItem(onSecondSetup, ...)
};

Storage<QString> storage;

const Group root {
    storage,                             // Top copy, 1st instance of StorageStruct
    onGroupSetup([storage] { ... }),     // Top copy is active
    Group {
        storage,                         // Nested copy, 2nd instance of StorageStruct,
                                         // shadows Top copy
        onGroupSetup([storage] { ... }), // Nested copy is active
    },
    Group {
        onGroupSetup([storage] { ... }), // Top copy is active
    }
};